Conventional batteries for vehicles such as automobiles, golf carts, etc., are known. These generally comprise a casing containing multiple cells with anodes, cathodes, and separator plates immersed in an electrolyte. One example would be a lead acid battery having a pair of terminals, the anodes and cathodes being made of lead or a lead alloy and the electrolyte containing sulfuric acid.
Typically, such batteries have a limited useful life as cycling can result in the eventual loss of water from the electrolyte through electrolysis, releasing hydrogen gas, and/or deposition of impurities which eventually result in short circuiting within the battery.
Methods for increasing battery life have centered on programmed watering schemes, to make up for water loss. However, such schemes have no effect on the deposition of materials that can short the battery, nor are such methods available for use with sealed batteries which are commonly sold for automotive uses.
Another problem that leads to shortened battery life is corrosion of the battery components, particularly of the electrodes with corresponding penetration damage to the separation medium typically included between the electrodes in the battery. This separating medium is microporous, being in essence, a permeable membrane which may mate on the cathode side to a fiber mat material, with progressive penetration of this medium by conductive particles enhancing the likelihood that shorting will occur. The cathodes and anodes, while normally designed with a degree of corrosion resistance, will nevertheless suffer corrosion damage over the life of the battery, which can, of course, shorten battery life as well as cause release of the conductive particles that may eventually migrate to and penetrate the separator medium.
One method proposed for controlling gas emissions from a battery was proposed in U.S. Pat. No. 3,928,066 to Lewenstein, where quatemary ammonium compounds were included in a lead-acid battery with antimony grids to reduce the evolution of hydrogen gas from the anode electrode of the battery.
In French Patent No. 2,236,283 to Bonnaterre, quaternary ammonium compounds were included in nickel-iron and nickel-cadmium batteries to reduce the evolution of oxygen gas from the cathode electrode of the battery.
While securing a reduction in the evolution of gas under idealized testing conditions, the measures disclosed do not provide a long term solution to battery life.
Prevention of dissolution of a zinc anode is described in U.S. Pat. No. 3,953,242 to Hoffman, in which a primary cell has as the sole electrolyte a quaternary ammonium salt of limited solubility. A disadvantage of the limited solubility is an increase in the internal resistance of the cell.
Reduction in self-discharge is described in U.S. Pat. No. 4,064,324 to Eustace, in which an electrochemical cell contains a water soluble salt which is converted into an insoluble complex with cathodic halogen. While prolonging the shelf life of the cell, the discharge characteristics are impaired.
In U.S. Pat. No. 3,660,170 to Rampel, zinc dendritic precipitation is inhibited in alkaline zinc batteries by using a cationic high molecular weight organic polymer, preferably in the form of a hydroxide polymer, which promotes smooth and non-dendritic electro-deposition of the zinc metal onto the electrode, the polymer present at 0.1 to 10 percent by weight.
The use of the above described additives may have secured a short term performance increase, but this was found to diminish with time. To date, none of the above patented inventions have achieved commercial acceptance.
What is needed is a method and apparatus to provide a reduction in water disassociation/gas evolution, to prevent or reduce depositions which can result in cell shorting, and/or to reduce corrosion of the battery components.